Engine

ABSTRACT

An engine 1 includes an exhaust manifold, an intake manifold, and an EGR device configured to supply EGR gas from the exhaust manifold to the intake manifold. An upper end of the EGR cooler extended downward is attached to a downwardly extending attachment part provided to the exhaust manifold.

TECHNICAL FIELD

The present invention relates to an engine including an EGR device.

BACKGROUND ART

There has been known an engine including an EGR device whichrecirculates part of exhaust gas to intake air. The EGR device lowerscombustion temperature by recirculating post-combustion exhaust gas witha low oxygen concentration (EGR gas) to the intake air. This drop in thecombustion temperature suppresses and reduces generation of nitrogenoxides. In general, the EGR gas is recirculated to the intake air afterbeing cooled by an EGR cooler.

Patent Literature 1 (hereinafter, PTL 1) below discloses a structureincluding an EGR cooler on a side of a cylinder block. A flange on anEGR gas inlet side of the EGR cooler is supported by an exhaustmanifold, and a flange on an EGR gas outlet side of the EGR cooler issupported by an exhaust gas communication pipe which is a memberseparate from the exhaust manifold. Further, Patent Literature 2(hereinafter, PTL 2) below discloses a structure in which an EGR cooleris fixed to the outside surface of an exhaust manifold by using twobands.

CITATION LIST Patent Literature

PTL 1: Japanese Patent No. 6067092

PTL 2: Japanese Patent No. 3633824

SUMMARY OF INVENTION Technical Problem

In PTL 1, a stress is applied to flanges of the EGR cooler due to adifference in thermal expansion of members which respectively support anEGR gas intake side and an EGR gas outlet side, and which are differentfrom each other. Meanwhile, PTL 2 requires multiple bands to support theEGR cooler, which leads to an increase in the number of members,consequently increasing the cost.

The present invention have been made in view of the above problems, andit is an object of the present invention to provide an engine capable ofsuppressing stress to flanges of an EGR cooler, which stress is causedby thermal expansion, while enabling a reduction of the number ofmembers.

Solution to Problem

An aspect of the present invention is an engine including an exhaustmanifold, an intake manifold, and an EGR device configured to supply EGRgas from the exhaust manifold to the intake manifold.

An upper end of the EGR cooler extended downward is attached to adownwardly extending attachment part provided to the exhaust manifold.

The above aspect of the present invention may be such that an EGR pipeextended from the EGR cooler to the intake manifold is partially formedinside the exhaust manifold.

The above aspect of the present invention may be such that the EGRcooler includes a cooling unit configured to cool the EGR gas, and aswitching valve configured to control an inflow of the EGR gas to thecooling unit.

The switching valve blocks the inflow of the EGR gas to the coolingunit, when the temperature of the EGR gas from the exhaust manifold isnot more than a predetermined temperature, and allows the inflow of theEGR gas to the cooling unit, when the temperature of the EGR gas fromthe exhaust manifold is higher than the predetermined temperature.

The above described aspect of the present invention may be such that theattachment part includes a first opening configured to supply the EGRgas from the exhaust manifold to the EGR cooler, and a second openingconfigured to supply the EGR gas from the EGR cooler to the EGR pipe.

The above described aspect of the present invention may be such that anupper end of the EGR cooler has a supply port into which the EGR gas issupplied and a discharge port from which the EGR gas is discharged, andthe EGR cooler has therein a U-shaped path that connects to the supplyport and the discharge port.

In the present invention, the EGR cooler is supported at only oneposition with respect to the exhaust manifold. Therefore, a stressapplied to the flange of the EGR cooler due to thermal expansion can besuppressed and reduced. Further, the number of members can be reduced,because there is no need for using separately provided bands to supportthe EGR cooler.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A perspective view of an engine according to an embodiment.

FIG. 2 A perspective view of the engine according to the embodiment.

FIG. 3 An exploded perspective view of an exhaust manifold and an EGRcooler.

FIG. 4 A diagram providing a top view, a front view, and a bottom viewof the exhaust manifold.

FIG. 5 A cross-sectional view schematically showing an EGR cooler.

EMBODIMENT OF EMBODIMENT

In the following, an embodiment of the present invention will bedescribed with reference to the drawings.

First, a schematic structure of the engine 1 is described with referenceto FIG. 1 and FIG. 2. It should be noted that, in the followingdescription, two sides parallel to a crankshaft 2 are referred to as theleft and right. A side where a cooling fan 8 is arranged is referred toas the front side. A side where a flywheel housing 9 is arranged isreferred to as the rear side. A side where an exhaust manifold 6 isarranged is referred to as the left side. A side where an intakemanifold 5 is arranged is referred to as the right side. A side where acylinder head cover 7 is arranged is referred to as the upper side. Aside where an oil pan 11 is arranged is referred to as the lower side.These expressions are used as the references of four directions and thepositional relation of the engine 1.

An engine 1 as a motor mounted to a work machine such as an agriculturalmachine and a construction machine includes a crankshaft 2 serving as anoutput shaft of the engine and a cylinder block 3 having therein apiston (not shown). On the cylinder block 3, a cylinder head 4 ismounted. On the right side surface of the cylinder head 4, an intakemanifold 5 is arranged. On the left side surface of the cylinder head 4,an exhaust manifold 6 is arranged. The top surface side of the cylinderhead 4 is covered by a head cover 7. The crankshaft 2 has its front andrear ends protruding from front and rear surfaces of the cylinder block3. On the front surface side of the engine 1, a cooling fan 8 isarranged. From the front end side of the crankshaft 2, rotational poweris transmitted to the cooling fan 8 through a cooling fan V-belt.

On the rear surface side of the engine 1, a flywheel housing 9 isarranged. The flywheel housing 9 accommodates therein a flywheel 10pivotally supported at the rear end side of the crankshaft 2. Therotational power of the engine 1 is transmitted from the crankshaft 2 tooperating units of the work machine through the flywheel 10. An oil pan11 for storing an engine oil is arranged on a lower surface of thecylinder block 3. The engine oil in the oil pan 11 is supplied tolubrication parts of the engine 1 through an oil pump (not shown) in thecylinder block 3, and then returns to the oil pan 11.

A fuel supply pump 13 is arranged below the intake manifold 5 on theright side surface of the cylinder block 3. Further, the engine 1includes injectors 14 for four cylinders. Each of the injectors 14 has afuel injection valve of electromagnetic-controlled type. By controllingthe opening/closing of the fuel injection valves of the injectors 14,the high-pressure fuel in a common rail is injected from the injectors14 to the respective cylinders of the engine 1.

On the front surface side of the cylinder block 3, a cooling water pump15 for supplying cooling water is arranged. The rotational power of thecrankshaft 2 drives the cooling water pump 15 along with the cooling fan8, through the cooling fan V-belt. With the driving of the cooling waterpump 15, the cooling water in a radiator (not shown) mounted to the workmachine is supplied to the cylinder block 3 and the cylinder head 4 andcools the engine 1. Then the cooling water having contributed to thecooling of the engine 1 returns to the radiator. Above the cooling waterpump 15, an alternator 16 is arranged.

The intake manifold 5 is connected to an intake throttle member 17. Thefresh air (outside air) suctioned by the air cleaner is subjected todust removal and purification in the air cleaner, and fed to the intakemanifold 5 through the intake throttle member 17, and then supplied tothe respective cylinders of the engine 1.

In an upper portion of the intake manifold 5, an EGR device 18 isarranged. The EGR device 18 is a device that supplies part of theexhaust gas of the engine 1 (EGR gas from the exhaust manifold 6) to theintake manifold 5, and includes an EGR pipe 21 connecting to the exhaustmanifold 6 through an EGR cooler 20 and an EGR valve case 19 thatcommunicates the intake manifold 5 to the EGR pipe 21.

A downwardly-open end portion of the EGR valve case 19 is bolt-fastenedto an inlet of the intake manifold 5 protruding upward from the intakemanifold 5. Further, a rightwardly-open end portion of the EGR valvecase 19 is coupled to an outlet side of the EGR pipe 21. By adjustingthe opening degree of the EGR valve member (not shown) in the EGR valvecase 19, the amount of EGR gas supplied from the EGR pipe 21 to theintake manifold 5 is adjusted. The EGR valve member is driven by anactuator 22 attached to the EGR valve case 19.

In the intake manifold 5, the fresh air supplied from the air cleaner tothe intake manifold 5 through the intake throttle member 17 is mixedwith the EGR gas (part of exhaust gas from the exhaust manifold 6)supplied from the exhaust manifold 6 to the intake manifold 5 throughthe EGR valve case 19. As described, by recirculating part of theexhaust gas from the exhaust manifold 6 to the engine 1 through theintake manifold 5, the combustion temperature is lowered and theemission of nitrogen oxide (NOX) from the engine 1 is reduced.

The EGR pipe 21 is connected to the EGR cooler 20 and the EGR valve case19. The EGR pipe 21 includes a first EGR pipe 21 a arranged on the rightside of the cylinder head 4, a second EGR pipe 21 b formed in a rear endportion of the cylinder head 4, and a third EGR pipe 21 c arranged onthe left side of the cylinder head 4.

The first EGR pipe 21 a is generally an L-shaped pipe. The first EGRpipe 21 a has its inlet side coupled to an outlet side of the second EGRpipe 21 b, and has its outlet side coupled to the EGR valve case 19.

The second EGR pipe 21 b is formed in such a manner as to penetratethrough the rear end portion of the cylinder head 4 in theleft-and-right directions as shown in FIG. 2. In other words, the secondEGR pipe 21 b and the cylinder head 4 are integrally formed. The secondEGR pipe 21 b has its inlet side coupled to an outlet side of the thirdEGR pipe 21 c, and has its outlet side connected to the inlet side ofthe first EGR pipe 21 a.

The third EGR pipe 21 c is formed inside the exhaust manifold 6. Inother words, the third EGR pipe 21 c and the exhaust manifold 6 areintegrally formed. With the third EGR pipe 21 c and second EGR pipe 21 bintegrally formed with the exhaust manifold 6 and the cylinder head 4,respectively, the space needed can be saved, and the pipes less likelyreceive an external impact.

FIG. 3 is an exploded perspective view of the exhaust manifold 6 and anEGR cooler 20. FIG. 4 is a diagram providing a top view, a front view,and a bottom view of the exhaust manifold 6. The exhaust manifold 6includes an aggregate part 61 configured to aggregate the exhaust gasfrom exhaust ports of the cylinders to one place and discharge theexhaust gas, an attachment part 62 protruding downward from the rear endof the aggregate part 61, and an EGR pipe unit 63 extended rearward fromthe attachment part 62. The third EGR pipe 21 c is formed in the EGRpipe unit 63.

The attachment part 62 of the exhaust manifold 6 includes a firstopening 62 a configured to supply EGR gas from the exhaust manifold 6 tothe EGR cooler 20, and a second opening 62 b configured to supply EGRgas from the EGR cooler 20 to the third EGR pipe 21 c. The first opening62 a and the second opening 62 b are aligned in the front-and-reardirection. The attachment part 62 has therein an EGR gas draw-outpassage 62 c communicating the aggregate part 61 with the first opening62 a.

The EGR cooler 20 has a substantially quadrangular prism shape extendedin the up-and-down direction. The EGR cooler 20 is attached to thedownwardly protruding attachment part 62 provided to the exhaustmanifold 6. An upper end of the EGR cooler 20 is bolt-fastened to theattachment part 62. In the present embodiment, the exhaust manifold 6 iscantilevered in such a manner as to be parallel (standing posture) tothe axis direction of the cylinders (not shown).

The upper end of the EGR cooler 20 has a supply port 20 a to which theEGR gas is supplied from the exhaust manifold 6, and a discharge port 20b from which the EGR gas is discharged to the third EGR pipe 21 c. Thesupply port 20 a and the discharge port 20 b are aligned in thefront-and-rear direction. The supply port 20 a is coupled to the firstopening 62 a of the exhaust manifold 6. The discharge port 20 b iscoupled to the second opening 62 b of the exhaust manifold 6. Further,inside the EGR cooler 20, a U-shape path connecting to the supply port20 a and the discharge port 20 b is formed. The EGR gas, after travelingdownward from the supply port 20 a makes a U-turn to travel upward,towards the discharge port 20 b. Thus, the EGR gas supplied from thesupply port 20 a to the EGR cooler 20 is discharged from the dischargeport 20 b through the U-shaped path.

Further, the EGR cooler 20 overlaps with a gear case cover 23 in a rearview, as shown in FIG. 2. The gear case cover 23 is arranged to face theflywheel housing 9, and covers a cam gear (not shown) together with theflywheel housing 9. Covering the cam gear with the gear case cover 23and the flywheel housing 9 blocks the sound. Therefore, gear noise canbe reduced. Since the EGR cooler 20 overlaps with the gear case cover23, the EGR cooler 20 is protected from an external impact(particularly, from an impact from the rear side).

FIG. 5 schematically provides a cross-sectional view of the EGR cooler20, and (a) shows a state where a switching valve 201 is closed, whereas(b) shows a state where the switching valve 201 is open. The arrow inthe diagram shows the flow of the EGR gas.

The EGR cooler 20 includes a cooling unit 20 c configured to cool theEGR gas and the switching valve 201 configured to control an inflow ofthe EGR gas to the cooling unit 20 c. The cooling unit 20 c is arrangedbelow the EGR cooler 20. By driving the cooling water pump 15, thecooling water is supplied around the cooling unit 20 c, thereby coolingthe EGR gas passing through the cooling unit 20 c.

When the temperature of the EGR gas from the exhaust manifold 6 is notmore than a predetermined temperature, the switching valve 201 closesthe passage to the cooling unit 20 c as shown in FIG. 5(a), and blocksthe inflow of the EGR gas to the cooling unit 20 c. This way, the EGRgas is not supplied to the cooling unit 20 c while the temperature ofthe EGR gas is low. Therefore, a quick warm up can be possible. On theother hand, when the temperature of the EGR gas from the exhaustmanifold 6 is higher than the predetermined temperature, the switchingvalve 201 opens the passage to the cooling unit 20 c as shown in FIG.5(b), and allows the inflow of the EGR gas to the cooling unit 20 c.This way, the EGR gas is supplied to the cooling unit 20 c, while thetemperature of the EGR gas is high. Therefore, the temperature of theEGR gas can be appropriately controlled.

An embodiment of the present invention has been described with referenceto the drawings. It, however, should be considered that specificconfigurations of the present invention are not limited to thisembodiment. The scope of this invention is indicated by the range ofpatent claims as well as the description of the enforcement formdescribed above, as well as the range of patent claims and even meaningand all changes within the range.

REFERENCE SIGNS LIST

-   1 engine-   3 cylinder block-   4 cylinder head-   5 intake manifold-   6 exhaust manifold-   18 EGR device-   20 EGR cooler-   20 c cooling unit-   21 EGR pipe-   62 attachment part-   201 switching valve

1. An engine, comprising: an exhaust manifold, an intake manifold, andan EGR device configured to supply EGR gas from the exhaust manifold tothe intake manifold, wherein an upper end of the EGR cooler extendeddownward is attached to a downwardly extending attachment part providedto the exhaust manifold.
 2. The engine according to claim 1, wherein anEGR pipe extended from the EGR cooler to the intake manifold ispartially formed inside the exhaust manifold.
 3. The engine according toclaim 1, wherein: the EGR cooler comprises a cooling unit configured tocool the EGR gas, and a switching valve configured to control an inflowof the EGR gas to the cooling unit, and the switching valve blocks theinflow of the EGR gas to the cooling unit, when the temperature of theEGR gas from the exhaust manifold is not more than a predeterminedtemperature, and allows the inflow of the EGR gas to the cooling unit,when the temperature of the EGR gas from the exhaust manifold is higherthan the predetermined temperature.
 4. The engine according to claim 2,wherein the attachment part comprises a first opening configured tosupply the EGR gas from the exhaust manifold to the EGR cooler, and asecond opening configured to supply the EGR gas from the EGR cooler tothe EGR pipe.
 5. The engine according to claim 1, wherein an upper endof the EGR cooler has a supply port into which the EGR gas is suppliedand a discharge port from which the EGR gas is discharged, and the EGRcooler has therein a U-shaped path that connects to the supply port andthe discharge port.